A microwave arrangement which can be operated as a power splitter and/or in a reciprocal manner also as power combiner is known from U.S. Pat. No. 5,223,809. In this context, coaxial lines are used to connect the inputs and outputs of the signal combiner and/or signal splitter correspondingly.
Power combiners and/or power splitters should be capable of being manufactured as cost favourably as possible, wherein the signals to be transmitted should only be minimally attenuated. Accordingly, power distributors and/or power combiners should generate very small throughput power losses. If such broadband amplifiers are operated as high-power amplifiers, low losses should be aimed for, especially in order to avoid the development of high levels of heat resulting from losses from the throughput attenuation.
Wilkinson signal splitters are also used as power splitters. The function of a Wilkinson signal splitter is based upon the λ/4-line transformation (λ=wavelength), wherein the power of a signal connected to a first signal port is subdivided to form signals of identical power at a second and third signal port. If reflections of the signal occur in one signal path because of a defect in the line and/or an error matching in the line wave-resistances, the respectively other signal path remains uninfluenced by this. The second signal port and the third signal port are accordingly decoupled from one another. The principle of a signal splitter can also be used in a reciprocal manner for a signal combiner.
Signal splitters which are constructed in multiple stages are used internally by the applicant to combine and/or split broadband signals. In this context, several λ/4-lines are connected to one another in order to realise an increasingly broad bandwidth. One disadvantage of these signal splitters constructed in multiple stages is the requirement, based on construction considerations, to vary the wave-resistance in each stage of the λ/4-lines contained in this stage. Accordingly, in a first stage of the signal splitter, in which both signal paths are transmitted on a common line portion, high line wave-resistances are required. The line wave-resistances decline progressively with higher stages of the signal part. This requirement means that lines must be introduced with a small line width in the first stage, which become steadily wider in the higher stages of the signal splitter.
A further disadvantage of the multi-stage signal splitters conventionally used internally by the applicant with small line widths in the first stage is that the only part of the main current flows though the ground surface on the second upper side of the substrate, which is also described as a current crowding effect. This effect means that the current flows primarily in the region of the ground surface directly below the microstrip line arranged on the first upper side of the substrate.
For these reasons, it is necessary to design signal splitters and/or signal combiners with relatively low line wave-resistances in the first stage.
In order to solve this problem, a relatively thicker substrate can be used, for example. Since the maximal thickness of the substrate should not exceed one tenth of the wavelength of the highest frequency to be transmitted, design limits are rapidly reached in this context. Such realizations are enormously cost intensive especially in high-frequency technology.
What is needed, therefore, is a microwave arrangement which transmits broadband signals with high powers and very high frequencies with in a low-loss manner.